System, method, and apparatus for applying transcutaneous electrical stimulation

ABSTRACT

A system, method, and apparatus for treating a medical condition by applying transcutaneous electrical stimulation to a target peripheral nerve of a subject. Electrical stimulation is applied to the peripheral nerve via a stimulation electrode pattern under closed-loop control in which EMG responses are monitored and used to adjust stimulation parameters. In response to detecting an unacceptable recording, electrical stimulation is applied to the peripheral nerve under open-loop control.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/725,755, filed on Aug. 31, 2018. This application also claims thebenefit of U.S. Provisional Application Ser. No. 62/751,173, filed onOct. 26, 2018. The subject matter of these applications is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to a wearable electronic medical device fortranscutaneous electrical stimulation of peripheral nerves for thepurpose of treating one or more medical conditions.

BACKGROUND

There are many known technologies that use electrical stimulation ofperipheral nerves to treat medical conditions. Implantable stimulationtechnologies require surgical implantation of stimulation leads, with apulse generator that is either surgically implanted or connectedexternally to wire leads. Percutaneous stimulation technologies are lessinvasive, but still require the stimulation electrodes to pierce theskin. While these technologies can be effective in treating certainconditions, they are less desirable due to their invasiveness andbecause they can require the continued or routine attention ofspecialists, requiring doctor's office visits, phone calls, etc.

SUMMARY

A system for applying transcutaneous electrical stimulation includes awearable, such as a garment, sock, sleeve, brace, strap, etc. Thewearable includes an electronic stimulator device that providestranscutaneous electrical stimulation to peripheral nerves for treatmentof medical conditions. Advantageously, the wearable allows the subjectto use the system at a time and place that is convenient. The subjectmay choose to use the device while they are at work or at home, or whilewalking, relaxing, or sleeping, as long as certain environments and/oractivities (e.g., wet environments/activities) are avoided. Since thereare no implantable or percutaneous components, the risk of infection,battery fault burns, and transcutaneous power transfer discomfort and/orbleeding, are greatly reduced or eliminated.

The wearable includes electrodes that are arranged in a predeterminedpattern or array, and that engage the subject's skin at desiredlocations when the wearable is worn. These skin surface mountedelectrodes can, for example, be similar to those of other transcutaneouselectrical nerve stimulation (“TENS”) units to implement high voltageskin surface electrical stimulation. The electrodes include stimulatingelectrodes and recording electrodes, which the wearable can position atthe same location or at different locations on the subject's skin. Infact, the identities of individual electrodes, i.e., stimulating orrecording, can change depending on the application/treatment for whichthe system is being used. The stimulating electrodes apply thetranscutaneous electrical stimulation to the subject's skin, and therecording electrodes record the electromyogram (EMG) responses elicitedby the stimulation.

The wearable also includes a control unit that is electrically connectedto the electrodes and that is operable to control electrical stimulationapplied by the stimulating electrodes and to control the recording ofEMG responses by the recording electrodes. The control unit executesclosed-loop control algorithms, which adjust stimulation patterns,periodically or constantly, based on the elicited EMG response from therecruited nerves as feedback. Alternatively, instead of the EMG responseproviding the closed-loop feedback, or as a supplement to the EMGresponse, the system can include alternative devices, such asmechanomyogram (MMG) devices (e.g., an accelerometer), or can implementelectronic measurements, such as electrode impedance, to implement theclosed-loop control.

This closed-loop control eliminates the need for “programming sessions”commonly required for neurostimulation systems. The day-to-dayvariability that arises due to electrode placement and skin impedancenecessitates these sessions to make sure that the electrodes arepositioned to provide adequate stimulation treatment. With the presentsystem, instead of physically adjusting the electrode positions on thesubject in order to find the arrangement that produces the desiredresponse, the system itself can select which electrodes to use, and canadjust the number and pattern of electrodes until an acceptable response(EMG and/or MMG) is achieved. Once the appropriate electrodes pattern isidentified, the order, intensity, timing, etc. of the stimulation can befurther tuned or adjusted to optimize the EMG and/or MMG response. Thesystem can tailor the electrical stimulation applied by eachindividually controllable electrode in the array so that the stimulationcharacteristics of each electrode (e.g., frequency, amplitude, pattern,duration, etc.) is configured to deliver the desired stimulation effect.This tailoring can be implemented automatically through the algorithm,which incrementally adjusts these characteristics, monitoring the and/orresponse at each increment until optimal settings are identified.Stimulation therapy can then be applied with these settings, accordingto the algorithm, which can be dictated by the requirements of thetreating physician.

Throughout the electrical stimulation treatment process, the system canimplement periodic or continuous measurement of system integrity. Onesuch measurement is that of electrode impedance to remove the risks thatcan arise when electrodes lift away from the skin or certain propertiesof the electrodes deteriorate. The impedance measurement capabilitycould also potentially be used to provide an indication of the optimalelectrode location for nerve stimulation. This may be the case, forexample, in areas where the skin is thin and where the stimulated nervesare most superficial. Thus, impedance values may be used as an input tothe closed-loop stimulation algorithm to adjust stimulation patterns. Byway of example, when stimulating the tibial nerve, the posterior area ofthe medial malleolus typically has comparatively thin skin and is thesite where tibial nerve is most superficial, which leads to its being agood candidate for measuring electrode impedance.

The control unit and the architecture of the system may be designed toconstantly optimize stimulation by monitoring the quality of nerverecruitment periodically or on a pulse-by-pulse basis, with the goal ofkeeping recruitment strength to a minimum (which can reduce muscletwitching) and to minimize the stimulation energy being deliveredthrough the skin. The EMG recording feature is capable of detecting bothM-wave and F-wave responses, which can be used as feedback inputs(together or independently) to the closed-loop stimulation algorithm todetermine the level of activation of the stimulated peripheral nerve. Asignificant aspect of the F-wave is that it provides an indication thatthe stimulation-evoked peripheral nerve action potential has activatedmotor neurons in the associated spinal cord nerves/nerve plexus. Forexample, an F-wave response to tibial nerve stimulation indicates thatthe tibial nerve action potential has activated motor neurons in thesacral spinal cord/sacral plexus.

The wearable transcutaneous electrical stimulation device can be used tostimulate various peripheral nerves in order to treat medical conditionsassociated with those nerves. For example, the system can be used toapply electrical stimulation to the tibial nerve to treat pelvic floordysfunction, e.g., overactive bladder (OAB) medical conditions. Asanother example, the system can be used to apply electrical stimulationto the tibial nerve to treat sexual dysfunction. In this manner, it isbelieved that tibial nerve stimulation could be used to treat genitalarousal aspects of female sexual interest/arousal disorder by improvingpelvic blood flow. In yet another example, the system can be used toapply electrical stimulation to the tibial nerve to treat plantarfasciitis.

As another example, the system can be applied to the wrist area toprovide stimulation to the ulnar nerve and/or median nerve. Thestimulation electrode array can, for example, be placed on the inside ofthe lower arm anywhere 0 to 20 cm from the wrist line, EMG recordingelectrodes can be placed on the base of thumb to record signal fromabductor/flexor pollicis brevis. EMG recording electrodes alternativelyor additionally can be placed on the base of pinky to record signal fromabductor/flexor digiti minimi brevis. The nerve activation could beconfirmed by recording M-wave and F-wave EMG signals from the relevantmuscles. The EMG signal can also be used as a control signal to adjustthe stimulation parameters or stimulation electrode patterns. Thistechnology can be applied to median nerve activation for pain managementin carpal tunnel syndrome, hypertension management, and nerve conductionstudy/nerve injury diagnosis for median/ulnar nerve neuropathy, etc.

As a further example, the system can be used to apply transcutaneouselectrical stimulation to provide neurostimulation to peripheral nervesin order to enhance nerve regeneration after peripheral nerve injury.

Implementing closed-loop control, the system can utilize measured EMGresponses to detect and obtain data related to the electrical activityof muscles in response to the applied stimulation. This data can be usedas feedback to tailor the application of the electrical stimulation.Additionally or alternatively, the system can also implement MMGsensors, such as accelerometers, to measure the physical response of themuscles. Other feedback, such as impedance measurements betweenelectrodes and other biopotential recording, can also be utilized.Through this closed-loop implementation, the system can utilizetechniques such as current steering and nerve localization to provideperipheral nerve stimulation therapy for treating various medicalconditions.

The system, method, and apparatus for applying transcutaneous electricalstimulation disclosed herein has many aspects, which can be included orutilized in various combinations.

According to one aspect, a method treats a medical condition by applyingtranscutaneous electrical stimulation to a target peripheral nerve of asubject.

According to another aspect, alone or in combination with any otheraspect, the method can include positioning a plurality of stimulationelectrodes on a skin surface proximate the targeted peripheral nerve,the stimulation electrodes being spaced from each other in apredetermined configuration. The method also can include positioning oneor more recording electrodes on a skin surface remote from thestimulation electrodes at a location where electromyogram (EMG)responses to electrical stimulation of the targeted peripheral nerve canbe detected. The method also can include stimulating the peripheralnerve by applying electrical stimulation pulses via a stimulationelectrode pattern selected from the plurality of stimulation electrodesaccording to stimulation parameters under closed-loop control in whichEMG responses to the electrical stimulation pulses are monitored via therecording electrodes and the stimulation parameters are adjusted inresponse to the monitored EMG responses. The method further can include,in response to detecting an unacceptable condition of the recordingelectrodes, applying electrical stimulation pulses via the stimulationelectrode pattern according to the stimulation parameters underopen-loop control in which the stimulation parameters are maintainedwithout adjustment.

According to another aspect, alone or in combination with any otheraspect, the unacceptable condition of the recording electrodes caninclude unacceptable impedance measurements.

According to another aspect, alone or in combination with any otheraspect, the step of applying electrical stimulation pulses further caninclude monitoring for mechanomyogram (MMG) responses to the electricalstimulation pulses and applying the electrical stimulation pulses underclosed-loop control in which the stimulation parameters are adjusted inresponse to the monitored MMG responses.

According to another aspect, alone or in combination with any otheraspect, the step of applying electrical stimulation pulses can includedetecting impedances of the recording electrodes and, in response todetecting acceptable impedances of the recording electrodes, applyingthe electrical stimulation pulses.

According to another aspect, alone or in combination with any otheraspect, the method can include: obtaining sample measurements via therecording electrodes, checking the sample measurements for noise,checking the sample measurements for voluntary EMG responses, applyingthe electrical stimulation pulses under closed-loop control in responseto determining an acceptable level of noise and the absence of voluntaryEMG responses, and applying the electrical stimulation pulses underopen-loop control in response to determining an unacceptable level ofnoise or the presence of voluntary EMG responses.

According to another aspect, alone or in combination with any otheraspect, each application of an electrical stimulation pulse underclosed-loop control can include: applying the electrical stimulationpulse, executing a time delay, recording EMG responses via the recordingelectrodes after the time delay is executed, and adjusting thestimulation parameters in response to the recorded EMG responses. Theduration of the time delay can be about 5 ms or less.

According to another aspect, alone or in combination with any otheraspect, adjusting the stimulation parameters in response to the recordedEMG responses under closed loop control can include: increasing theamplitude of subsequent stimulation pulses in response to the recordedEMG responses being below a predetermined EMG window, decreasing theamplitude of subsequent stimulation pulses in response to the recordedEMG responses being above the predetermined EMG window, and maintainingthe amplitude of subsequent stimulation pulses in response to therecorded EMG responses being within the predetermined EMG window.

According to another aspect, alone or in combination with any otheraspect, each application of an electrical stimulation pulse underopen-loop control can include: applying the electrical stimulationpulse, and executing a time delay having a duration sufficient tomaintain a constant stimulation period. The duration of the time delaycan be about 75 ms.

According to another aspect, alone or in combination with any otheraspect, the stimulation electrode pattern can be selected from a patternlist, wherein the method further can further include generating thepattern list by:

-   -   a) identifying a set of predetermined stimulation electrode        patterns, each stimulation electrode pattern identifying which        of the plurality of stimulation electrodes will apply the        electrical stimulation pulses, and each stimulation electrode        pattern having associated with it the stimulation parameters        according to which it applies stimulation pulses;    -   b) selecting a stimulation electrode pattern from the set of        predetermined stimulation electrode patterns;    -   c) generating a stimulation pulse using the selected stimulation        electrode pattern according to its associated stimulation        parameters;    -   d) determining via the recording electrodes whether the        stimulation pulse using the selected stimulation electrode        pattern elicited an EMG response;    -   e) adding the selected stimulation electrode pattern to the        pattern list in response to detecting an EMG response;    -   f) omitting the selected stimulation electrode pattern from the        pattern list in response to not detecting an EMG response; and    -   repeating steps b) through f) for each stimulation electrode        pattern in the set of predetermined stimulation electrode        patterns to complete the pattern list.

According to another aspect, alone or in combination with any otheraspect, the method can include optimizing the stimulation electrodepatterns in the pattern list by:

-   -   g) adjusting the stimulation parameters for each stimulation        electrode pattern in the pattern list to attempt to elicit an        improved EMG response;    -   h) selecting a stimulation electrode pattern from the set of        predetermined stimulation electrode patterns;    -   i) generating a stimulation pulse using the selected stimulation        electrode pattern according to its associated stimulation        parameters;    -   j) determining via the recording electrodes whether the        stimulation pulse using the selected stimulation electrode        pattern elicited an EMG response;    -   k) adding the selected stimulation electrode pattern to the        pattern list in response to detecting an EMG response;    -   l) omitting the selected stimulation electrode pattern from the        pattern list in response to not detecting an EMG response; and    -   repeating steps h) through l) for each stimulation electrode        pattern in the set of predetermined stimulation electrode        patterns to complete the pattern list. Steps h) through l) can        be repeated until each electrode pattern in the pattern list is        optimized.

According to another aspect, alone or in combination with any otheraspect, the method can also include ordering the stimulation electrodepatterns in the pattern list according to their elicited EMG and/or MMGresponses.

According to another aspect, alone or in combination with any otheraspect, stimulating the peripheral nerve can include stimulating thetibial nerve. Stimulating the peripheral nerve can include stimulatingthe tibial nerve at a location between the medial malleolus and theAchilles tendon.

According to another aspect, alone or in combination with any otheraspect, monitoring EMG responses can include recording EMG signals thatresult from recruitment of the tibial nerve's motor fibers. This caninclude positioning the recording electrodes on the bottom of thesubject's foot near the abductor hallucis and the flexor hallucis brevisto record the EMG signals.

According to another aspect, alone or in combination with any otheraspect, stimulating the peripheral nerve can treat overactive bladder,sexual dysfunction, or plantar fasciitis.

According to another aspect, alone or in combination with any otheraspect, stimulating the peripheral nerve can include stimulating theulnar nerve and/or median nerve for pain management in carpal tunnelsyndrome, hypertension management, and nerve conduction study/nerveinjury diagnosis for median/ulnar nerve neuropathy, etc. Stimulating theulnar nerve and/or median nerve can treat carpal tunnel syndrome orhypertension. Stimulating the ulnar nerve and/or median nerve to performa nerve conduction study or nerve injury diagnosis.

According to another aspect, alone or in combination with any otheraspect, stimulating the ulnar nerve and/or median nerve can includepositioning the stimulating electrodes on the inside of the lower arm 0to 20 cm from the wrist line, and recording EMG responses can includepositioning the recording electrodes on the base of thumb to recordsignal from abductor/flexor pollicis brevis, and/or positioning therecording electrodes on the base of pinky to record signal fromabductor/flexor digiti minimi brevis.

According to another aspect, alone or in combination with any otheraspect, stimulating the peripheral nerve can include applying theelectrical stimulation pulses to the peripheral nerve to enhance nerveregeneration after peripheral nerve injury.

According to another aspect, alone or in combination with any otheraspect, a system for treating overactive bladder by applyingtranscutaneous electrical stimulation to the tibial nerve of a subjectcan include a plurality of electrical stimulation electrodes, thestimulation electrodes being spaced from each other in a predeterminedconfiguration, one or more recording electrodes, a structure forsupporting the stimulation electrodes and the recording electrodesspaced apart from each other, and a control unit for controlling theoperation of the stimulation electrodes and the recording electrodes.The control unit can be configured to perform the method according toany of the aspects disclosed herein, alone or in combination with anyother aspect.

According to another aspect, alone or in combination with any otheraspect, an apparatus for applying electrical stimulation includes aplurality of electrical stimulation electrodes spaced from each other ina predetermined configuration, one or more recording electrodes, astructure for supporting the stimulation electrodes and the recordingelectrodes spaced apart from each other, and a control unit forcontrolling the operation of the stimulation electrodes and therecording electrodes. The control unit is configured to energize thestimulation electrodes under closed-loop control using the recordingelectrodes to measure feedback, energize the stimulation electrodesunder open-loop without measuring feedback, and determine whether toenergize the stimulation electrodes under closed-loop control oropen-loop control based on determining whether the feedback measured bythe recording electrodes is reliable.

According to another aspect, alone or in combination with any otheraspect, the structure can include a wearable structure configured toposition the stimulation electrodes in the proximity of a peripheralnerve and to position the recording electrodes in the proximity of amuscle activated by the peripheral nerve.

According to another aspect, alone or in combination with any otheraspect, the wearable structure can position the stimulation electrodesproximate the peripheral nerve and the recording electrodes proximate alocation where EMG signals that result from recruitment of theperipheral nerve's motor fibers can be detected.

According to another aspect, alone or in combination with any otheraspect, the wearable structure can include a strap, wherein thestimulation electrodes and recording electrodes are positioned atdifferent locations along the length of the strap. The strap can beconfigured to have a portion wrapped around the subject's ankle toposition the stimulating electrodes proximate the tibial nerve betweenthe medial malleolus and the Achilles tendon. The strap can also beconfigured to have a portion wrapped around the subject's foot toposition the recording electrodes on the bottom of the subject's footnear the abductor hallucis and the flexor hallucis brevis.

According to another aspect, alone or in combination with any otheraspect, the wearable structure can include a brace comprising an upperportion upon which the stimulation electrodes are positioned and a lowerportion upon which the recording electrodes are positioned. The upperportion of the brace can be configured to be wrapped around thesubject's ankle to position the stimulating electrodes proximate thetibial nerve between the medial malleolus and the Achilles tendon. Thelower portion of the brace can be configured to be wrapped around thesubject's foot to position the recording electrodes on the bottom of thesubject's foot near the abductor hallucis and the flexor hallucisbrevis.

According to another aspect, alone or in combination with any otheraspect, the apparatus can also include an accelerometer supported by thesupport structure adjacent or near the recording electrodes, wherein thecontrol unit can be configured to determine whether to energize thestimulation electrodes under closed-loop control or open-loop controlbased on acceleration values determined by the accelerometer.

According to another aspect, alone or in combination with any otheraspect, the control unit can include a microcontroller, a stimulatoroutput stage controlled by the microcontroller, and at least one analogoutput switch operatively connected to the stimulator output stage andcontrolled by the microcontroller. The stimulator output stage caninclude a plurality of channels for providing electrical current to thestimulating electrodes via the output switch, wherein each channel ofthe output stage includes a current source and current sink, and whereinthe microcontroller is configured to actuate the output switch toselectively identify which stimulation electrodes are active and toassign a channel of the output stage with each active stimulationelectrode, wherein the output stage associated with each stimulatingelectrode determines whether the stimulating electrode operates as ananode or a cathode.

According to another aspect, alone or in combination with any otheraspect, the microcontroller can be configured to determine amplitude andtiming values for the current source and current sink for each channelof the output stage and their associated active stimulation electrodes.

According to another aspect, alone or in combination with any otheraspect, the apparatus can include an impedance measurement circuit thatis operatively connected to the stimulator output stage and isconfigured to measure electrode impedances.

According to another aspect, alone or in combination with any otheraspect, the apparatus can include at least one analog input switch thatis operatively connected to the microcontroller, wherein themicrocontroller is configured to operate the analog input switch todetermine which of the recording electrodes are used to measurefeedback.

According to another aspect, alone or in combination with any otheraspect, the apparatus can include an analog front end circuit that isoperatively connected to the analog input switch, wherein the analogfront end is configured to facilitate sampling the recording electrodesat a predetermined sample rate in order to determine whether thefeedback measured by the recording electrodes is reliable. The samplerate can be 1,000-8,000 samples per second.

According to another aspect, alone or in combination with any otheraspect, the microcontroller can be configured to initiate via the analogfront end a sampling window after energizing the stimulation electrodes,wherein during the sampling window the recording electrodes are used tomeasure feedback signals to determine whether EMG data is present.

According to another aspect, alone or in combination with any otheraspect, the apparatus can include a radio for communicating wirelesslywith an external device for programming the microcontroller,uploading/downloading data, and remotely monitoring and/or controllingoperation of the control unit.

According to another aspect, alone or in combination with any otheraspect, a method for treating overactive bladder can include applyingtranscutaneous electrical stimulation to the tibial nerve of a subject.The method can include positioning a plurality of stimulation electrodeson a skin surface at a location between the medial malleolus and theAchilles tendon proximate the tibial nerve, the stimulation electrodesbeing spaced from each other in a predetermined configuration. Themethod also can include positioning one or more recording electrodes ona skin surface remote from the stimulation electrodes at a location onthe bottom of the subject's foot near the abductor hallucis and theflexor hallucis brevis muscles to record electromyogram (EMG) responsesthat result from recruitment of the tibial nerve's motor fibers. Themethod also can include stimulating the tibial nerve by applyingelectrical stimulation pulses via a stimulation electrode patternselected from the plurality of stimulation electrodes according tostimulation parameters under closed-loop control in which EMG responsesto the electrical stimulation pulses are monitored via the recordingelectrodes and the stimulation parameters are adjusted in response tothe monitored EMG responses. The method further can include, in responseto detecting an unacceptable condition of the recording electrodes,applying electrical stimulation pulses via the stimulation electrodepattern according to the stimulation parameters under open-loop controlin which the stimulation parameters are maintained without adjustment.

According to another aspect, alone or in combination with any otheraspect, a system for treating overactive bladder by applyingtranscutaneous electrical stimulation to the tibial nerve of a subjectcan include a plurality of electrical stimulation electrodes, thestimulation electrodes being spaced from each other in a predeterminedconfiguration, one or more recording electrodes, a structure forsupporting the stimulation electrodes and the recording electrodesspaced apart from each other, and a control unit for controlling theoperation of the stimulation electrodes and the recording electrodes.The control unit can be configured to perform the method according toany of the aspects disclosed herein, alone or in combination with anyother aspect.

DRAWINGS

FIG. 1A illustrates a left-foot implementation of an electronic medicaldevice for delivering transcutaneous electrical stimulation ofperipheral nerves, according to a first example configuration.

FIG. 1B illustrates a right-foot implementation of the electronicmedical device for delivering transcutaneous electrical stimulation ofperipheral nerves, according to the first example configuration.

FIG. 2A is an inner surface plan view of the electronic medical deviceof FIGS. 1A and 1B.

FIG. 2B is an outer surface plan view of the electronic medical deviceof FIGS. 1A and 1B.

FIGS. 2C-E are outer surface plan views of the electronic medical deviceof FIGS. 1A and 1B illustrating sequential steps in preparing the devicefor use.

FIG. 3A illustrates a left-foot implementation of an electronic medicaldevice for delivering transcutaneous electrical stimulation ofperipheral nerves, according to a second example configuration.

FIG. 3B illustrates a right-foot implementation of the electronicmedical device for delivering transcutaneous electrical stimulation ofperipheral nerves, according to the second example configuration.

FIG. 4A is an inner surface plan view of components of the electronicmedical device of FIGS. 3A and 3B.

FIG. 4B is an outer surface plan view of the components of theelectronic medical device of FIGS. 3A and 3B.

FIG. 4C is an outer surface plan view, taken from a first side,illustrating the components of FIGS. 4A and 4B assembled to form theelectronic medical device of FIGS. 3A and 3B.

FIG. 4D is an outer surface plan view, taken from a second side,opposite the first side, illustrating the components of FIGS. 4A and 4Bassembled to form the electronic medical device of FIGS. 3A and 3B.

FIG. 5 is a schematic block diagram of a control unit portion of theelectronic medical device.

FIG. 6 is a diagram illustrating example electrode arrangements forportions of the electronic medical device.

FIG. 7 is a flow chart illustrating an example nerve localizationprocess implemented by the electronic medical device.

FIG. 8 is a series of charts illustrating examples of recorded EMGresponses to electrical nerve stimulation.

FIG. 9 is a flow chart illustrating an example open-loop and closed-loopelectrical nerve stimulation processes implemented by the electronicmedical device.

DESCRIPTION

An electronic medical device, a system including the medical device, anda method for using the medical device, is configured to applytranscutaneous electrical stimulation to peripheral nerves to treatvarious medical conditions.

For example, the system can be used to stimulate the tibial nerve(transcutaneous tibial nerve stimulation “TTNS”) to treat medicalconditions associated with pelvic floor dysfunction, e.g., over-activebladder (OAB). In a TTNS implementation, the electronic medical deviceapplies electrical stimulation near the medial malleolus, whichactivates both sensory and motor fibers in the nerve. The activation ofthe sensory fibers of the tibial nerve helps to treat the urge-relatedsymptoms of OAB. The activation of the motor fibers can, however, causeunwanted side effects, such as toe twitch or spasm.

As another example, the system can be used to apply electricalstimulation to the tibial nerve to treat sexual dysfunction. In thismanner, it is believed that tibial nerve stimulation could be used totreat genital arousal aspects of female sexual interest/arousal disorderby improving pelvic blood flow.

As another example, the system can be applied to the wrist area toprovide stimulation to the ulnar nerve and/or median nerve for painmanagement in carpal tunnel syndrome, hypertension management, and nerveconduction study/nerve injury diagnosis for median/ulnar nerveneuropathy, etc.

The system and/or the device employed by the system can have a varietyof implementations. According to one implementation, the electronicmedical device (i.e., the electrodes, control unit, wiring, etc.) can befixed to a garment that is worn by the subject. The garment can be tightor snug-fitting so as to maintain sufficient contact between thesubject's skin and can be configured to position the electrodes atlocations specific to the peripheral nerves being stimulated. Forexample, to stimulate peripheral nerves in the area of the foot orankle, such as the tibial nerve near the medial malleolus as describedabove, the garment can be in the form of a sock, ankle brace, strap,sleeve, or other like structure. For stimulating peripheral nerves onthe leg, the garment can be a brace, strap, or sleeve sizedappropriately for lower leg, knee, or upper leg positioning. For knee orankle positioning, the garment can be configured, e.g., with openings,slots, or interconnected sections, to allow for bending with the jointwhile maintaining electrode positioning and contact.

Similarly, for stimulating peripheral nerves on the hand, the garmentcan be in the form of a glove, mitten, hand brace, or sleeve. Forstimulating peripheral nerves on the arm, the garment can be atight/snug fitting brace, strap, or sleeve (e.g., neoprene) that issized appropriately for lower arm (forearm/wrist), elbow, or upper armpositioning. For wrist and/or elbow positioning, the sleeve can beconfigured, e.g., via openings, slots, or interconnected sections, toallow for bending with the joint while maintaining electrode positioningand contact.

In keeping with the above, it will be appreciated that the manner inwhich the electronic medical device can be secured or supported on thesubject can vary. It will also be appreciated that the manner in whichthe electronic medical device is supported is not critical, as long ascontact between the electrodes and the subject's skin is maintained, thepositions of the electrode on the subject are maintained, and that theaforementioned are achieved in a manner that is comfortable to thesubject.

Strap Implementation

FIGS. 1A-B illustrate a system comprising an example configuration ofthe electronic medical device 10 for providing transcutaneous electricalnerve stimulation, referred to herein as a neurostimulator, supported ona subject 12. The neurostimulator 10 of FIGS. 1A-B includes a garment inthe form of a strap 20 that supports the neurostimulator and itscomponents on the subject 12. In the example configuration of FIGS.1A-B, the strap 20 connects the neurostimulator 10 to the subjects foot14, with FIG. 1A illustrating a left foot implementation, and FIG. 1Billustrating a right foot implementation. In both instances, the strap20 is wrapped figure-eight style, with one loop extending around thefoot and one loop extending around the lower leg/ankle. Opposite endportions of the strap 20 can be interconnected, e.g., via a buckle orloop 22 and an end portion 24 of the strap that extends through theloop, is folded over, and connected to itself with a hook and loopfastener. The hook and loop fastener is shown in FIG. 2B and includes ahook portion 26 and loop portion 28.

The strap 20 implementation of the neurostimulator 10 is advantageous inthat it is versatile and can be adapted to secure the neurostimulator toa wide variety of locations on the subject 12. The strap 20 can easilybe wrapped around the foot 14 and/or ankle 16, as shown, and can also bewrapped around and secured to any location along the length of thesubject's leg 18, either in a single loop or more than one loop, as thelength of the strap permits. At the knee, the strap 20 can be wrapped,for example, in a figure-eight style in a manner similar to thatillustrated in FIGS. 1A and 1B.

Referring to FIGS. 2A-B, the neurostimulator 10 includes a several ofcomponents that are secured or otherwise supported on the strap 20. Thesecurement of these components can be achieved in a variety of manners,such as by adhesives, stitching, mechanical fastening, hook and loopfasteners, or a combination thereof.

The neurostimulator 10 includes stimulation electrodes 50 that arearranged in one or more arrays 52 and positioned on an inner surface 36of the strap 20 at a widened end portion 30 of the strap. The number ofstimulation electrodes 50, the area covered by the array 52, theelectrode density (i.e., number of electrodes per unit area) in thearray, and the distribution or pattern of electrodes within the arrayall can vary depending on the intended application of theneurostimulator 10. Additionally, the neurostimulator 10 can includemore than one stimulation electrode array 52 again, depending on theapplication. In the example configuration of FIG. 2A, the stimulationelectrode array 52 includes six stimulation electrodes 50 arranged in agenerally elongated kidney-shaped manner. The number and arrangement ofthe stimulation electrodes 50, and the location/position of theelectrode array 52 on the strap 20 are by way of example only and are byno means limiting.

In the example configuration of FIG. 2A, the stimulation electrodes 50can be dry electrodes, in which case the neurostimulator 10 can includea removable/replaceable stimulation gel pad 54 shaped and sized tocoincide with and cover the stimulation electrode array 52. In use, thegel pad 54 facilitates a strong, reliable electrical connection betweenthe stimulation electrodes 50 and the subject's skin.

The neurostimulator 10 also includes dedicated recording electrodes 60that are arranged in one or more arrays 62 and positioned on the innersurface 36 of the strap 20 spaced from the stimulation electrode array52. The spacing between the stimulation electrodes 50 and the recordingelectrodes 60 can be important, as it can be necessary to provideadequate distance between the electrodes so that electrical stimulationsignals can be separated or distinguished from responses (e.g.,neurological, muscular, neuromuscular, etc.) to those electricalstimulation signals. This facilitates utilizing responses to stimulationsensed by the recording electrodes 60 as feedback in a closed-loopstimulation control scheme, which is described in detail below.

The number of recording electrodes 60, the area covered by the array 62,the electrode density (i.e., number of electrodes per unit area) in thearray, and the distribution or pattern of electrodes within the arrayall can vary depending on the intended application of theneurostimulator 10. Additionally, the neurostimulator 10 can includemore than one recording electrode array 62 again, depending on theapplication. In the example configuration of FIG. 2A, the recordingelectrode array 62 includes four electrodes 60 arranged linearly in twoparallel rows of two electrodes. The number and arrangement of therecording electrodes 60, and the location/position of the electrodearray 62 on the strap 20 are by way of example only and are by no meanslimiting.

In the example configuration of FIG. 2A, like the stimulation electrodes50, the recording electrodes 60 can also be dry electrodes. Because ofthis, the neurostimulator 10 can also include a removable/replaceablegel pad 64 shaped and sized to coincide with and cover the recordingelectrode array 62. In use, the gel pad 54 facilitates a strong,reliable electrical connection between the recording electrodes 60 andthe subject's skin.

Referring to FIG. 2B, the neurostimulator 10 also includes an electroniccontrol unit 70 that is operative to control the application oftranscutaneous electrical nerve stimulation via the stimulatingelectrodes 50 and to receive stimulation feedback gathered by therecording electrodes 60. The control unit 70 is located at the widenedend 30 of the strap 20 on an outer surface 38, opposite the innersurface 36, of the strap 20. The buckle 22 can be a portion of thecontrol unit 70 or can be connected to the control unit. In the exampleconfiguration of FIG. 2B, the control unit 70 has a generally elongatedkidney-shaped configuration similar to that of the stimulating electrodearray 52 and is positioned on the outer surface 38 generally oppositethe stimulating electrode array. This is by no means necessary to thedesign of the neurostimulator 10, as the shape and location of thecontrol unit 70 can vary.

In the example configuration of FIG. 2B, however, the shape and thepositioning of the control unit 70 is convenient. The control unit 70 isdetachably connected to the remainder of the neurostimulator 10 via aplug-in or snap-in connector 72 (see FIG. 2B), which receives a matingconnector 74 (see FIG. 2D) on the control unit 70. FIG. 2B shows thecontrol unit 70 connected to the neurostimulator 20 via the connector72, and FIG. 2C shows the neurostimulator 20 with the control unitdetached from the connector and removed. Configuring the control unit 70to be detachable/removable allows the control unit to be utilized withother neurostimulator configurations and also allows the strap 20 andthe components remaining on the strap (e.g., the electrodes, etc.) to bereplaced when worn out, expired, or otherwise due for replacement.

Advantageously, the stimulating electrode array 52 can be part of anassembly in which the stimulating electrodes 50 can be mounted on asubstrate or housing 56 constructed, for example of plastic. Thissubstrate/housing 56 can itself be secured to the strap 20 (e.g., viaadhesives, stitching, or mechanical fastening) to thereby secure thestimulation electrode array 52 to be strap. Forming the stimulatingelectrode array 52 in this manner facilitates a precise arrangement andspacing of the stimulation electrodes 50 and makes it easy to securethem to the strap 20.

The connector 72 can also be formed as a portion of the housing 56. Theconnector 72 can be configured to protrude from a side of the housing 56opposite the stimulation electrodes 50. The connector 72 can, forexample, extend through a hole in the strap 20 to position the connectoron or extending from the outer surface 38. When the control unit 70 isconnected to the connector 72, the strap 20 can be positioned betweenthe control unit and the portion of the housing 56 supporting thestimulator electrode array 52.

The connector 72 can support a plurality of terminals for electricallyconnecting the control unit 70 to the stimulation electrodes 50 and therecording electrodes 60. Certain terminals in the connector 72 can beelectrically connected to the stimulation electrodes 50 by wires orleads that are embedded within the plastic housing material (e.g., viainsert molding). Embedding the leads in this manner helps maintainadequate spacing between the conductors, which avoids the potential forshorts in the circuitry.

Other terminals in the connector can be electrically connected to therecording electrodes 60 by wires or leads 66 that are partially embeddedwithin the plastic housing material (e.g., via insert molding) and passthrough the housing 56, extending to the feedback electrode arrays 62.Through this configuration, all of the necessary electrical connectionsto the stimulation and recording electrodes 50, 60 are made when thecontrol unit 70 is installed on the connector 72.

The neurostimulator 10 also includes electrode backing 80 thatfacilitates safe storage and portability of the system. Fold lines 82,84 shown in FIG. 2A indicate lines along which the neurostimulator10/strap 20 can be folded to place the device in the stored condition.The steps involved in placing the neurostimulator 10 in the storedcondition are illustrated in FIGS. 2C-2E.

As shown in FIG. 2C, the control unit 70 is detached from the housing56. The control unit 70 is secured to the end portion 24 of the strap 20by the hook and loop fastener 26, 28. Next, as shown in FIG. 2D, withthe inner surface 36 facing up, the widened end portion 38 is foldedover along the fold line 82, which places the stimulating electrodearray 52 on a corresponding portion of the electrode backing 80. Next,as shown in FIG. 2E, the strap 20 is folded over along the fold line 84,which places the recording electrode array 62 on a corresponding portionof the electrode backing 80. This leaves the neurostimulator 10 in thestored condition of FIG. 2E.

To use the neurostimulator 10, the strap 20 is simply unfolded and thecontrol unit 70 is connected to the housing 56 via their respectiveconnectors 72, 74. The hook and loop fastener 26, 28 can bedisconnected, the strap 20 wrapped around the appropriate anatomy of thesubject, and the fastener re-connected to attach neurostimulator 10 tothe subject. Conveniently, where the neurostimulator 10 is configuredfor stimulating the tibial nerve in the position illustrated in FIGS.1A-B, the widened end 30 of the strap 20 can include a visual alignmentcue 90, such as a hole in the strap, that becomes aligned with themedial malleolus of the ankle when the stimulating electrodes areproperly positioned.

Brace Implementation

FIGS. 3A-B illustrate a system comprising another example configurationof an electronic medical device 110 for providing transcutaneouselectrical nerve stimulation, referred to herein as a neurostimulator,supported on a subject 112. The neurostimulator 110 of FIGS. 3A-1Bincludes a garment in the form of a brace 120 that supports theneurostimulator and its components on the subject 112. In the exampleconfiguration of FIGS. 3A-B, the brace 120 connects the neurostimulator110 to the subject's foot 114, with FIG. 3A illustrating a left footimplementation, and FIG. 3B illustrating a right foot implementation. Inboth instances, the brace 120 has an upper portion 130 wrapped aroundthe lower leg/ankle and a lower portion 150 portion wrapped around thefoot/ankle. Each of these portions are secured to the subject via aconnection such as a hook and loop fastener.

The brace 120 implementation of the neurostimulator 10 is advantageousin that it is versatile in its ability to position the stimulatingelectrodes and recording electrodes at different locations on thesubject. For example, stimulating electrodes can be positioned on theupper portion 130 of the brace 120 wrapped around the ankle, andrecording electrodes can be positioned on the lower portion 150 of thebrace wrapped around the foot. This can be especially advantageous forclosed-loop neurostimulation of the tibial nerve. In thisimplementation, stimulating electrodes on the upper portion 130 can belocated between the medial malleolus and the Achilles tendon to provideelectrical stimulation to the tibial nerve. Recording electrodes on thelower portion 150 can be located on the bottom of the subject's foot,near the flexor muscles (abductor hallucis and the flexor hallucisbrevis) for the big toe and can record the EMG signals that result fromrecruitment of the tibial nerve's motor fibers.

As another advantage, the brace 120 is configured for placement at orabout a subject's joint and provides for movement of that joint. Whilethe brace 120 is illustrated as being applied at the subject's anklejoint, it will be appreciated that the brace 120 can also be applied atthe knee joint or elbow joint. Additionally, positioning the brace 120at a joint is not critical, as it can be seen that the brace can beapplied at any location along the subject's arms or legs, sizepermitting.

The construction of the neurostimulator 110 is illustrated in FIGS.4A-D. For the example configuration of FIGS. 4A-D the upper portion 130and lower portion 150 of the strap 120 are separate components that areinterconnected by adjustment bands 122. The adjustment bands 122 canallow for adjusting the spacing between the upper and lower portions130, 150, e.g., via a buckle or hook and loop fastener, or the bands canbe of a fixed size amongst a range of sizes, e.g., x-small, small,medium, large, x-large, etc. The respective sizes of the upper and lowerportions 130, 150 can be similarly sized. In fact, the upper portion 130can itself be composed of first and second portions 132, 134 connectedby a band 136 that allows for adjusting the spacing between the upperand lower portions 130, 150, e.g., via a buckle or hook and loopfastener.

The upper portion 130 of the brace 120 includes a hook and loop fastenercomposed of a hook portion 140 and a loop portion 142, which arepositioned opposite each other along an upper extent of the upperportion. The upper portion 130 also includes opposite tab portions 144to which the adjustment tabs 122 (see, FIGS. 4C-D) are connected, e.g.,via stitching. Similarly, the lower portion 130 of the brace includes ahook and loop fastener composed of a hook portion 152 and a loop portion154, which are positioned opposite each other along a lower extent ofthe lower portion. The lower portion 150 also includes opposite tabportions 156 to which the adjustment tabs 122 (see, FIGS. 4C-D) areconnected, e.g., via stitching.

The neurostimulator 110 includes a several of components that aresecured or otherwise supported on the brace 120. The securement of thesecomponents can be achieved in a variety of manners, such as byadhesives, stitching, mechanical fastening, hook and loop fasteners, ora combination thereof. FIGS. 4A and 4B illustrate the neurostimulator110 in a partially assembled condition, with the electronic componentsof the neurostimulator mounted on the brace 120 prior to the first andsecond portions 132, 134 being interconnected by the adjustment bands122. This construction is advantageous because it allows the electroniccomponents of the neurostimulator 110 to be assembled onto brace 120while the upper and lower portions 130, 150 lie flat. The lying flatillustration of FIGS. 4A-B is for purposes of simplicity as it allowsthe upper and lower portions 130, 150 to be illustrated lying flat. FIG.4A illustrates an inner surface 124 of the brace 120. FIG. 4Billustrates an outer surface 126 of the brace 120.

The neurostimulator 110 includes stimulation electrodes 170 that arearranged in one or more arrays 172 and positioned on the inner surface124 of the upper portion 130 of the brace 120. In the exampleconfiguration illustrated in FIG. 4A, the stimulation electrode arrays172 are positioned on opposite sides of the adjustment band 136connecting the first and second portions 132, 134 of the upper portion130. This arrangement can, for example, allow the brace 130implementation of the neurostimulator 110 to be ambidextrous.

The number of stimulation electrodes 170, the area covered by thestimulation electrode arrays 172, the electrode density (i.e., number ofelectrodes per unit area) in the arrays, and the distribution or patternof electrodes within the array all can vary depending on the intendedapplication of the neurostimulator 110. In the example configuration ofFIG. 4A, each stimulation electrode array 172 includes six stimulationelectrodes 170 arranged in a generally rectangular manner in two rows ofthree electrodes. The number and arrangement of the stimulationelectrodes 170, and the location/position of the electrode array 172 onthe brace 120 are by way of example only and are by no means limiting.

In the example configuration of FIG. 4A, the stimulation electrodes 170can be dry electrodes, in which case the neurostimulator 110 can includeone or more removable/replaceable stimulation gel pads 174 shaped andsized to coincide with and cover the stimulation electrode array 172. Inuse, the gel pads 174 facilitate a strong, reliable electricalconnection between the stimulation electrodes 170 and the subject'sskin.

The neurostimulator 110 also includes recording electrodes 180 that arearranged in one or more arrays 182 and positioned on the inner surface124 of the lower portion 150 of the brace 120 at a location spaced fromthe stimulation electrode arrays 172. The spacing between thestimulation electrodes 170 and the recording electrodes 180 can beimportant, as it can be necessary to provide adequate distance betweenthe electrodes so that electrical stimulation signals can be separatedor distinguished from responses (e.g., neurological, muscular,neuromuscular, etc.) to those electrical stimulation signals. Thisfacilitates utilizing responses to stimulation sensed by the recordingelectrodes 180 as feedback in a closed-loop stimulation control schemewhich, again, is described in detail below.

The number of recording electrodes 180, the area covered by the array182, the electrode density (i.e., number of electrodes per unit area) inthe array, and the distribution or pattern of electrodes within thearray all can vary depending on the intended application of theneurostimulator 110. In the example configuration of FIG. 4A, there aretwo recording electrode arrays 182, each of which includes two recordingelectrodes 180 arranged linearly. The number and arrangement of therecording electrodes 180, and the location/position of the electrodearrays 182 on the brace 120 are by way of example only and are by nomeans limiting.

In another implementation, the neurostimulator 110 can be configured toinclude MMG sensors (e.g., accelerometers) for sensing muscle movementas opposed to electrical activity. The optional MMG sensors areillustrated in dashed lines at 186 in FIG. 4A. In this implementation,the MMG sensors 186 can be implemented in addition to or in place of,the EMG electrodes 180. Implementing the MMG 186 sensors along with theEMG sensors 180 can prove beneficial in that the combination can provideadditional functionality. For example, the MMG sensor 186 can be used toconfirm the validity of an EMG measured feedback response. Additionally,the MMG sensors 186 (or any other accelerometer for that matter) can beused to verify that the subject in a resting, i.e., not moving,condition prior to initiating a therapy session.

In the example configuration of FIG. 4A, like the stimulation electrodes170, the recording electrodes 180 can also be dry electrodes. Because ofthis, the neurostimulator 110 can also include a removable/replaceablerecording gel pad 184 shaped and sized to coincide with and cover therecording electrode arrays 182. In use, the gel pad 184 facilitates astrong, reliable electrical connection between the recording electrodes180 and the subject's skin.

Referring to FIG. 4B, the neurostimulator 110 also includes anelectronic control unit 200 that is operative to control the applicationof transcutaneous electrical nerve stimulation via the stimulatingelectrodes 170 and to receive stimulation feedback gathered by therecording electrodes 180. The control unit 200 is located on the outersurface 126 of the upper portion 130 adjacent the adjustment band 136and opposite one of the stimulating electrode arrays 172 on the innersurface 124 of the upper portion. In the example configuration of FIG.4B, the control unit 200 has a generally elongated racetrack-shapedconfiguration similar, to that of the stimulating electrode arrays 172,although narrower. This is by no means necessary to the design of theneurostimulator 110, as the shape and location of the control unit 200can vary.

In the example configuration of FIG. 4B, however, the shape and thepositioning of the control unit 200 is convenient. The control unit 200can be detachably connected to the remainder of the neurostimulator 110via a plug-in or snap-in connector, such as by a connector (not shown)that is similar or identical to the connector associated with thecontrol unit of the example configuration of FIGS. 2A-D. Configuring thecontrol unit 200 to be detachable/removable allows the control unit tobe utilized with other neurostimulator configurations and also allowsthe brace 120 and the components remaining on the brace (e.g., theelectrodes, etc.) to be replaced when worn out, expired, or otherwisedue for replacement.

Advantageously, each stimulating electrode array 172 can be part of anassembly in which the stimulating electrodes 170 can be mounted on asubstrate or housing 176 constructed, for example of plastic. Thissubstrate/housing 176 can itself be secured to the brace 120 (e.g., viaadhesives, stitching, or mechanical fastening) to thereby secure thestimulation electrode array 172 to be brace. Forming the stimulatingelectrode array 172 in this manner facilitates a precise arrangement andspacing of the stimulation electrodes 170 and makes it easy to securethem to the brace 120.

In a manner similar or identical to that of the example configuration ofFIGS. 2A-D, the connector of each stimulating electrode array 172 canalso be formed as a portion of the housing 176. The connector can beconfigured to protrude from a side of the housing 176 opposite thestimulation electrodes 170. The connector can, for example, extendthrough a hole in the brace 120 to position the connector on orextending from the outer surface 126. When the control unit 200 isconnected to the connector, the brace 120 can be positioned between thecontrol unit and the portion of the housing 176 supporting thestimulator electrode array 172.

Again, in a manner similar or identical to that of the exampleconfiguration of FIGS. 2A-D, the connector can support a plurality ofterminals for electrically connecting the control unit 200 to thestimulation electrodes 170 and the recording electrodes 180. Certainterminals in the connector can be electrically connected to thestimulation electrodes 170 by wires or leads that are embedded withinthe plastic housing material (e.g., via insert molding). Embedding theleads in this manner helps maintain adequate spacing between theconductors, which avoids the potential for shorts in the circuitry.

Other terminals in the connector can be electrically connected to therecording electrodes 180 by wires or leads 184 that are partiallyembedded within the plastic housing material (e.g., via insert molding)and pass through the housing 176, extending to the recording electrodearrays 182. Through this configuration, all of the necessary electricalconnections to the stimulation and recording electrodes 170, 180 aremade when the control unit 200 is installed on the neurostimulator 110.

Referring to FIGS. 4C-D, the neurostimulator 110 is assembled byconnecting the first and second portions 132, 134 of the upper portion130 with the adjustment band 136. The upper and lower portions 130, 150are interconnected by two adjustment bands 122 that interconnect theirrespective tab portions 144, 156. This completes the assembly of theneurostimulator 110, placing it in a condition to be worn by the subjectin the manner illustrated in FIGS. 3A-B.

To use the neurostimulator 110, the brace 120 is simply unfolded and thecontrol unit 200 is connected to the housing 176 via the connectors. Thehook and loop fasteners 140, 142 and 152, 154 are disconnected, thebrace 120 wrapped around the appropriate anatomy of the subject. InFIGS. 3A-B, the upper portion 130 is wrapped around the lower leg/ankle112 of the subject, and the lower portion 150 is wrapped around the foot114 of the subject. The hook and loop fasteners 140, 142 and 152, 154are re-connected to attach neurostimulator 110 to the subject.Conveniently, where the neurostimulator 110 is configured forstimulating the tibial nerve in the position illustrated in FIGS. 3A-B,the upper portion 130 of the brace 120 can include visual alignment cues210, such as holes in the brace, that become aligned with the medialmalleolus of the ankle when the stimulating electrodes 170 are properlypositioned.

Control Unit Configuration

The control units 70, 200 of the example configurations of theneurostimulator 10, 110 of FIGS. 1A-4D can have a variety ofconfigurations. An example configuration for the control units 70, 110is shown in FIG. 5. Referring to FIG. 5, the control unit 70, 200includes a microcontroller 220 powered by a primary or rechargeablebattery 222 via a battery protection and charging circuit 224. Thecircuit 224 offers battery protection typical for a medical device, suchas over-current and over-voltage protection, under-voltage protection,and a charging controller. An external cable or charging cradle 226charges the battery 222 via the circuit 224. Alternatively, the battery222 can be charged wirelessly, e.g., via a wireless charging cradle. Apushbutton 228 cycles on/off power to the control unit 70, 200.

The battery protection and charging circuit 224 also marshals power to ahigh voltage power supply circuit 230, a digital power supply circuit232, and an analog power supply circuit 234. The high-voltage powersupply circuit 230 is used to provide a stimulation compliance voltageto the output stage's current sources and sinks. Since this device is atranscutaneous stimulator, it can require a compliance voltage in therange of about 40-200 V or more in order to provide the necessarycurrent to stimulate the tibial nerve. For this embodiment, a compliancevoltage of 120 volts is used for the compliance voltage.

A radio controller 240, such as a Bluetooth® or Zigbee® radiocontroller, provides a communication input to the microcontroller 220for functions such as programming the control unit 70, 200,uploading/downloading data, and monitoring/controlling theneurostimulator 10, 110 during use. The radio controller 240 could, forexample, pair the microcontroller to an enabled device, such as asmartphone, tablet, or computer, executing software that enables theuser to monitor or otherwise control the operation of theneurostimulator 10, 110. The microcontroller 220 controls the operationof indicators 242, such as LEDs, that indicate the state or condition ofthe control unit 70, 210. The microcontroller 220 can control anaccelerometer 244, which can provide input to determine whether theneurostimulator 10, 110, and thus the subject, is moving or at rest.

The microcontroller 220 is responsible for controlling the stimulationoutput, measuring the electrode impedance, and processing the EMGresponse. The microcontroller 220 runs software for performing thesefunctions, including decision-making algorithms to allow the device toprovide the desired therapy. The microcontroller 220 controls theoperation of an amplitude control circuit 250, a timing control circuit252, and a digital-to-analog converter (DAC) 254. By “circuit,” it ismeant that these functions can be implemented in any desired manner,e.g., through discrete components, integrated circuits, or a combinationthereof. The amplitude control circuit 250, timing control circuit 252,and DAC 254 drive a stimulator output stage 260, which providesstimulator output signals (e.g., pulse-width-modulated “PWM” outputsignals) to one or more analog output switches 262. The outputswitch(es) 262 are operatively connected to a port 280 comprising aplurality of terminals (E1-E8 in FIG. 5) that facilitates connecting thecontrol unit 70, 200 to the stimulator and recording electrodes, forexample, via the leads 66, 184 (see, FIGS. 2A and 4B, respectively).Through this connection via the leads 66, 184, the stimulator outputstage 260 can be operatively connected to the stimulator electrodes 50,170.

The microcontroller 220 receives electrode impedance values via animpedance measurement circuit 264 that is operatively connected to thestimulator output stage 260. The microcontroller 220 also receiveselectrode feedback values (e.g., F-wave and M-wave values) via an analogfront end 270 that is operatively connected to one or more analog inputswitches 272. The input switch(es) 272 are also operatively connected tothe terminals/port 280 and can thereby receive feedback from therecording electrodes 60, 180 that facilitates connecting the controlunit 70, 200 to the stimulator and recording electrodes, for example,via the leads 66 (see, FIG. 2A) or 184 (see, FIG. 4B).

The impedance measurement circuit 264 allows for measuring the impedanceof the electrodes. It is important to measure the impedance often, incase one or more of the electrodes begins to lift from the skin. Thereare two potential hazards related to electrode lifting that should bemitigated. First, if an electrode is partially lifted from the skin, thesurface area of the electrode that is in contact with the skin isreduced and the current density of the stimulation current is increased,which can be unsafe. Second, if an active electrode is completely liftedfrom the skin, a brief but large amount of energy can be delivered tothe tissue when the electrode makes contact with the skin, which canresult in pain.

Electrode impedances measured via the impedance measurement circuit 264can also be used as an additional input for a closed-loop stimulationoptimization algorithm.

The stimulator output stage 260 provides the current to the stimulatingelectrodes via the output switch 262. Each channel of the output stageincludes a current source and current sink, which allows each channel toprovide either a positive or negative current to the tissue through thecorresponding stimulation electrode(s) 50, 170. In this configuration,each current source and sink can have independently programmableamplitude control 250 and timing control 252, which provides thecapability to “steer” the current applied via the stimulation electrodes50, 170, as described below. The programmable range can vary dependingon the application, and is selected to be capable of achieving thedesired nerve recruitment. In an example configuration, the currentsources can have a programmable range from zero to +20 milliamperes(mA), and the current sinks can have a programmable range from zero to−20 mA.

As shown in FIG. 5, the analog output switches 262 and input switches272 can both be operatively connected to each of the terminals E1-E8.Through operation of the switches 262, 272 as commanded by themicrocontroller 220, the identity or role of the terminals, i.e., outputterminal or input/feedback terminal, can be actively identified. Thisallows the microcontroller 220 to selectively identify, activate, anddeactivate electrodes in a desired pattern, order, combination, etc.,according to the particular therapy regimen being applied. This alsoallows the therapy to be tailored, for example, in response to signalsreceived from the recording electrodes.

Control Overview

According to one example implementation, the neurostimulator 10, 100described above can control the application of stimulation therapyaccording to two general phases: nerve localization and stimulationdelivery. These two phases work synergistically to provide thefunctionality set forth in the following paragraphs.

During the nerve localization phase, the target peripheral nervestructure, e.g., the tibial nerve, is localized when the neurostimulator10, 100 is donned and activated. In the nerve localization phase, theneurostimulator 10, 100 implements a process in which the followingfunctions are performed:

-   -   Ramping up stimulation energy across various electrode patterns.    -   Monitoring EMG response after each stimulation pulse.    -   Determining the electrode pattern and stimulation parameters        that optimally activate the target peripheral nerve.

During the stimulation delivery phase, electrical stimulation isdelivered to the target peripheral nerve structure using the electrodepattern(s) and stimulation parameters determined during the nervelocalization phase. In the stimulation delivery phase, theneurostimulator 10, 100 implements a process in which the followingfunctions are performed:

-   -   Deliver stimulation pulses to the target peripheral nerve.    -   Continuously optimize the delivery of stimulation pulses, which        includes:        -   Monitoring EMG response after each stimulation pulse.        -   Monitoring electrode impedance.        -   Adjusting either the electrode pattern (current-steering) or            stimulation energy to optimize recruitment of the tibial            nerve.    -   Automatically stopping stimulation at the end of the therapy        session.

The nerve localization and stimulation delivery phases are described inmore detail in the following sections.

Nerve Localization

In practice, the control unit 110 can be programmed with a set ofelectrode patterns that identify which stimulation electrode 50, 170 inan electrode array 52, 172 are active, and also the polarity or type,i.e., anode (+) or cathode (−) assigned to the electrode. FIG. 6illustrates an example configuration for an electrode array 52, 172 anda chart illustrating an example set of electrode patterns. In theexample illustrated in FIG. 6, the electrode array 52, 172 has eightelectrodes 50, 170, identified at E1-E8, and the chart identifies tendifferent electrode patterns (patterns 1-10) for the electrode array.For each electrode pattern, each electrode is identified as being acathode (C), anode (A), or inactive (blank). Thus, for example, inpattern 3, electrodes E1 and E2 are cathodes, electrodes E5 and E6 areanodes, and electrodes E3, E4, E7, and E8 are inactive. While there area large number of patterns that are possible with an eight-electrodearray, the patterns can effectively be narrowed down to a shorter list,such as the illustrated 10 patterns or more, depending on the nerveunder recruitment.

The neurostimulator 10, 110 can be configured to perform a nervelocalization routine to determine which of the electrode patterns shouldbe utilized on a subject. In the example configuration of FIG. 6, theelectrode array 52, 172 can be specifically designed, i.e., shaped andelectrodes positioned, to stimulate the tibial nerve in the regionbetween the medial malleolus and the Achilles tendon. The electrodearray 52, 172 can be configured to perform stimulation on this or otherregions where peripheral nerve stimulation is desired.

In the example configuration of FIG. 6, the electrode array 52, 172 iscurved to allow the medial malleolus to be used as a placement guide.Also, the array can be symmetrical so that it can be placed on eitherankle. The electrode arrangement within the array must be configured tocapture the tibial nerve, meaning that the nerve must pass below orbetween at least one pair of electrodes. If the tibial nerve passesoutside the extents of the array, activation of the tibial nerverequires much higher stimulation energies, or it may not be possible toactivate the tibial nerve at all.

The purpose of using an array for stimulation (as opposed to a singlepair of electrodes) is to create an optimized stimulation field forrecruiting the target (e.g., tibial) nerve. If the stimulation field istoo small, the nerve will not be recruited and therapy will not bedelivered. If the stimulation field is too large, too many motor neuronswill be recruited resulting in undesired effects, such as pain,twitching, or muscle spasm. In order to optimize the stimulation field,the ability to steer current using multiple electrodes if preferred. Forexample, electrode pattern 8 assigns electrodes E3 and E4 as anodes andelectrodes E7 and E8 as cathodes. Viewing the arrangement of theseelectrodes 50, 170 on the array 52, 172, it can be seen that the use ofthis electrode pattern could be effective on a nerve path that passesdirectly adjacent or between these electrode pairs.

By selecting the appropriate stimulation electrodes 50, 170 from thestimulation electrode arrays 52, 172, and varying the amplitude andpolarity of the current applied via the selected electrodes, theelectric field applied to the subject can be shaped so that the currentis steered to the target nerves. By shaping the field, theneurostimulator 10, 100 can automatically adjust to day-to-day donningand placement variability for a given subject. Current steering alsoallows the neurostimulator 10, 100 to work across a subject populationwith wide anatomical variation, for example providing a shallow fieldfor subjects with nerves that are superficial to the skin, or apenetrating field for subjects with nerves that are deep. In theillustrated example configurations, the stimulation electrode arrays 52,152 include six electrodes. Any number of stimulation electrodes greaterthan one can be used. In general, the “field steering” capability of theneurostimulator 10, 100 increases with the number of stimulatingelectrodes 50, 170 that are included.

Because there will be session-to-session variability in the location ofthe stimulating electrode array 52, 172 due to the don/doff process, aswell as variability in skin/tissue impedance, providing open-loopstimulation applying rigid pre-programmed stimulation parameters couldbe disadvantageous, often providing too little or too much stimulationenergy to recruit the nerve. Advantageously, the nerve localizationalgorithm is executed at the beginning of each therapy session todetermine which of the preprogrammed electrode patterns will be mosteffective.

FIG. 7 illustrates a flowchart showing the method or process 300implemented by the nerve localization algorithm. The steps in theprocess 300 are not meant to be exclusive, i.e., other steps can beincluded. Nor is the process 300 intended to be strictly followed interms of the order shown in FIG. 7 or described herein. The process 300illustrates steps, perhaps a minimum, necessary to localize theperipheral nerve that is to be stimulated.

It should be noted here that, the process 300 is a closed-loop algorithmthat utilizes feedback recorded via the recording electrodes 60, 180 tomake determinations and/or adjust settings. As such, the process 300relies on utilization of the feedback to determine which of theelectrode patterns effectively achieves nerve recruitment. Specifically,the process 300 relies on feedback from the recording electrodes 60, 180to provide indication of EMG response feedback. Alternatively, theprocess 300 can rely on accelerometers to provide MMG response feedback.

Referring to FIG. 7, the process 300 begins at step 302, where animpedance measurement is performed in order to determine which, if any,of the electrodes E1-E8 have open or prohibitively high impedance. Thisstep 302 can be considered an integrity check for the electrodes 50, 170in the array 52, 172 to determine if any of the electrodes in the arrayare not sufficiently contacted with the skin. If any of the electrodesin the array are determined to be performing in a substandard manner,indicated by displaying an open (infinitely high) or sufficiently highimpedance, those electrodes and the electrode patterns that utilizethose electrodes can be eliminated from use.

For example, in the example of FIG. 6, it can be seen from row 2 thatelectrode E6 has high impedance. In this instance, electrode patterns 3,6, 7, and 9 are eliminated form use in the current therapy session.Alternatively, the algorithm could instruct the control unit to providesome indication to the user, such as an alarm or display, to re-positionor adjust the electrodes to see if contact can be improved.

To avoid interfering with stimulation and EMG measurement, the integritycheck at step 302 can be completed in a short amount of time, such as 25milliseconds or less. Also, the impedance measurement can be conductedso as to cause little or no sensation in the subject's skin. Therefore,the excitation current for performing the integrity check should below-amplitude, such as 1 mA or less. For the integrity check 302, theimpedance value at each electrode is not critical. Instead, determiningwhether the impedance is below a certain threshold is adequate.

Additionally, conditions other than high or low impedance can bedetermined in this integrity check. For example, indicators such asdry/wet contact checks, whole/brittle/fractured contact checks, contactsurface area checks, and contact reflectance checks can be made duringthe connectivity evaluation. Sensors, such as don/doff, stretch, strain,bending or contact sensors (via electrical, optical or mechanical means)can also be used for conducting the connectivity evaluation. Thesesensors could also be incorporated into a buckle, clasp, snap, hook/eyeor zipper feature.

Once the integrity check is performed, the process 300 proceeds to step304 where the first electrode pattern (that hasn't been eliminated bythe integrity check) is loaded. The process 300 then proceeds to step306 where the neurostimulator 10, 110 generates stimulation pulse(s)using the electrode pattern loaded in step 304. The process 300 proceedsnext to step 310, where a determination is made as to whether thestimulation pulses generated at step 306 elicited an EMG response, i.e.,feedback measured via the recording electrodes. Step 310 canadditionally or alternatively determine whether there is a MMG responsewhere the feedback devices include accelerometer(s).

If, at step 310, EMG (or MMG) is not detected, the process 300 revertsto step 314, where a new electrode pattern is loaded. The process 300then proceeds to step 306, as described above. If, at step 310, EMG (orMMG) is detected, the process 300 proceeds to step 312, where theelectrode pattern is added according to pattern selection rules. Theprocess 300 then proceeds to step 316, where a determination is made asto whether the current electrode pattern is the last electrode patternin the list.

The pattern selection rules at step 312 for adding an electrode patterncan be defined to prioritize electrode patterns identified as being thebest suited to recruit the target nerves. These pattern selection rulesmay be implemented as follows:

-   -   If one pattern is significantly better than the others (e.g., as        determined from the EMG data, see below), that pattern should be        used as the primary pattern moving forward.    -   If two or three patterns are roughly equivalent, any one of the        patterns can be used as the primary pattern. Moving forward,        this pattern can be switched to other ones if the nerve        recruitment displayed by the current primary pattern begins to        diminish.    -   If the nerve recruitment for a particular pattern begins to        diminish and increasing the stimulation parameters does not fix        the problem, similar patterns can be re-introduced to the        algorithm.

If, at step 316, it is determined that the current electrode pattern isnot the last pattern in the list, the process 300 reverts to step 314,where a new electrode pattern is loaded. The process 300 then proceedsto step 306, as described above. If, at step 316, it is determined thatthe current electrode pattern is the last pattern in the list, thisindicates that the pattern list is complete. The process 300 proceeds tostep 320 where the stimulation parameters for the electrode patterns inthe pattern list are optimized. At step 320, the stimulation parameters(e.g., frequency, amplitude, pattern, duration, etc.) are updated tooptimize the nerve recruitment for each pattern. The process 300 thenreverts back to the initial step at 302 and proceeds as described above.If the recruitment for a given electrode pattern improves, thestimulation parameters are kept. If not, they revert back to previousvalues. This process repeats itself until the pattern list is filledwith electrode patterns optimized for nerve recruitment.

From the above, it will be appreciated that the nerve localizationprocess 300 determines which of the electrode patterns to utilize andwhich to discard for any given stimulation therapy session, and thenoptimizes the stimulation parameters for the utilized patterns. Theexecution of this process 300 is fast. During execution, theneurostimulator 10, 110 applies stimulation therapy pulses via thestimulating electrodes 50, 170 and monitors for EMG responses via therecording electrodes 60, 180 after each pulse.

The analog front end circuit 270 can replace traditional EMG measurementcircuitry such as a filter, amplifier, rectifier, and/or integrator. Thecontrol unit 110 utilizes the analog front-end circuit 270 to sample therecording electrodes at a predetermined sample rate, such as 1,000-8,000samples per second. The EMG sampling window will begin after thestimulation pulse is finished, and the window will last for apredetermined brief period, such as 8-90 milliseconds. The resulting EMGdata, comprised of M-wave or F-wave or both, will be analyzed using aFast Fourier Transform (FFT) technique that clearly shows if EMG ispresent.

To execute the process 300 of FIG. 7, the neurostimulator 10, 110monitors for electromyogram (EMG) signals via the recording electrodes60, 180 in response to stimulation applied via the stimulationelectrodes 50, 170. FIG. 8 illustrates examples of the EMG responsesthat can be recorded, which include: No EMG Response, F-wave Response,M-wave Response, and M and F-wave Response. In the example where no EMGresponse is recorded, the stimulation pulse artifact can be seen on theleft, with no response following. In the example where an M-waveresponse is recorded, the stimulation pulse artifact can be seen on theleft, followed by the M-wave at about 6 to 10 ms post-stimulation. Inthe example where an F-wave response is recorded, the stimulation pulseartifact can be seen on the left, followed by the F-wave responses atabout 50 to 55 ms post-stimulation. In the example where both an M-waveand F-wave responses are recorded, the stimulation pulse artifact can beseen on the left, followed by the M-wave and F-wave at 6 to 10 ms andabout 50 to 55 ms post-stimulation, respectively. These response timescould change slightly, depending on a variety of factors, such as thehydration and/or salinity of the subject tissue, the arrangement andspacing of the electrodes, and the characteristics of the stimulationsignals.

For each of the four recorded response scenarios, FIG. 8 alsoillustrates a corresponding Fast Fourier Transform (FFT) results for theraw post-artifact signal. The FFT results are calculated by themicrocontroller 220 and are used in the process 300 to determine whetheran EMG response is present (see, step 310 in FIG. 7).

Stimulation Delivery

The neurostimulator 10, 110 can apply stimulation therapy using anopen-loop control scheme, a closed-loop control scheme, or a combinationof open-loop and closed-loop control schemes, depending on the controlalgorithm programmed into the microcontroller 220. For open-loopcontrol, the control units 70, 200 can apply electrical stimulation viathe stimulation electrodes 50, 170 according to settings (frequency,amplitude, pattern, duration, etc.) without regard to any feedbackmeasured via the recording electrodes 60, 180. This is not to say thatfeedback is not measured, just that, in an open-loop control scheme, thefeedback is not used to inform or control the algorithm executed by themicrocontroller 220 to control the application of stimulation therapy.In a closed-loop control scheme, the neurostimulator 10, 110 implementsa control algorithm in which feedback from the recording electrodes 60,180 informs and helps control the application of stimulation therapy.

FIG. 9 illustrates by way of example a process 400 by which theneurostimulator 10, 110 controls the application of electrical nervestimulation using the electrode pattern(s) identified by the nervelocalization process 300 of FIG. 7. The stimulation control process 400can employ both open-loop and closed-loop control, with closed-loopsteps or portions of the process being illustrated in solid lines andopen-loop steps or portions being illustrated in dashed lines. Ideally,the process 400 will proceed with closed-loop control, as it is able toutilize feedback to optimize the application of stimulation therapy.

The process 400 begins at step 402, where the impedances of therecording electrodes 60, 180 are checked. If, at step 404, it isdetermined that the recording electrode impedances are too high (e.g.,resulting in unavailable or unreliable feedback), the process 400 thenshifts to open-loop mode (see dashed lines) and proceeds to step 412,where a delay is implemented. The purpose of delay 412 is to assist inmaintaining a constant stimulation period, meaning that the duration ofdelay 412 should be equal to the duration of closed-loop step 406. Aftercompleting delay 412, the process 400 proceeds to step 414, where thestimulation electrode impedances are checked.

At step 404, if the impedances of the recording electrodes areacceptable, the process 400 remains in closed-loop mode and proceeds tostep 406, where samples are obtained via the recording electrodes tocheck for significant noise or voluntary EMG responses. At step 410, ifnoise or EMG are present, the feedback is considered unreliable and theprocess 400 shifts to open-loop mode and proceeds to step 414. At step410, if significant noise or voluntary EMG is not present, the feedbackis considered reliable and the process 400 remains in closed-loop modeand proceeds to step 414.

At step 414, regardless of whether the process is in open-loop mode orclosed-loop mode, the impedances of the stimulation electrodes 50, 170are checked. At step 416, if the stimulation electrode impedances areacceptable, the process 400 proceeds to step 420 and the neurostimulator10, 110 generates stimulation pulses, which are applied via thestimulation electrodes using the optimal electrode pattern, asdetermined by the nerve localization process 300 (see FIG. 7). If, atstep 416, the stimulation electrode impedances are too high, the process400 proceeds to step 420 and the neurostimulator 10, 110 generatesstimulation pulses that are applied via the stimulation electrodes usingan alternative electrode pattern selected from the pattern listdetermined by the nerve localization process 300. In either case, aftergenerating the stimulation pulse using the optimal pattern (step 420) orthe alternative pattern (step 422), the process 400 proceeds to step424.

At step 424, the process 400 implements a pre-recording delay to allowtime for the electrical stimulation applied at step 420 or 422 to elicitan EMG response. As discussed above, these delays can be relativelyshort, so the delay at step 424 can, likewise, be short, e.g., 5 ms orless. If the process 400 is in open loop mode, it proceeds to step 432,where a further delay is implemented. This delay 432 should match theduration of closed-loop steps 426 and 430 so that a constant stimulationperiod is maintained. If the process 400 is in closed-loop mode, itproceeds to step 426 and checks for feedback via the recordingelectrodes 60, 180. The process 400 then proceeds to step 430, where anydetected EMG feedback signals are recorded and analyzed.

At this point, regardless of whether the process 400 is in open-loopmode (step 432) or closed-loop mode (step 430), the process proceeds tostep 434, where a determination of whether the number of stimulationpulses applied in the current therapy session has reached apredetermined number (N). If the predetermined number (N) of pulses havenot yet been applied, the process proceeds to step 436, the stimulationamplitude is maintained at the current level, and the process 400reverts back to step 402, where the impedance of the recordingelectrodes is checked and the process 400 repeats. If, at step 434, thepredetermined number (N) of pulses has been reached, the process 400proceeds to step 440.

At step 440, if the process 400 in open-loop mode, the process proceedsto step 442, the stimulation amplitude is maintained at the currentlevel, and the process 400 reverts back to step 402, where the impedanceof the recording electrodes is checked and the process 400 repeats. Atstep 440, if the process 400 is not in open-loop mode (i.e., is inclosed-loop mode), the process proceeds to step 444, where adetermination is made as to whether the EMG recorded at step 430 isbelow a predetermined window, i.e., below a predetermined range ofacceptable EMG values. If the EMG is below the predetermined window, theprocess 400 proceeds to step 446, where the stimulation amplitude isincreased for the next pulse, if permitted. The process 400 then revertsback to step 402, where the impedance of the recording electrodes ischecked and the process 400 repeats with the increased stimulationamplitude.

If, at step 444, the EMG is not below the window, the process 400proceeds to step 450 where a determination is made as to whether the EMGis above the predetermined window. If the EMG is above the predeterminedwindow, the process 400 proceeds to step 452, where the stimulationamplitude is decreased for the next pulse. The process 400 then revertsback to step 402, where the impedance of the recording electrodes ischecked and the process 400 repeats with the decreased stimulationamplitude. If, at step 450, the EMG is not above the predeterminedwindow, the EMG is determined to be within the predetermined window andthe process 400 proceeds to step 454, where the stimulation amplitude ismaintained at the current level for the next pulse. The process 400 thenreverts back to step 402, where the impedance of the recordingelectrodes is checked and the process 400 repeats.

While aspects of this disclosure have been particularly shown anddescribed with reference to the example aspects above, it will beunderstood by those of ordinary skill in the art that various additionalaspects may be contemplated. A device or method incorporating any of thefeatures described herein should be understood to fall under the scopeof this disclosure as determined based upon the claims below and anyequivalents thereof. Other aspects, objects, and advantages can beobtained from a study of the drawings, the disclosure, and the appendedclaims.

1. A method for treating overactive bladder by applying transcutaneouselectrical stimulation to the tibial nerve of a subject, comprising:positioning a plurality of stimulation electrodes on a skin surface at alocation between the medial malleolus and the Achilles tendon proximatethe tibial nerve, the stimulation electrodes being spaced from eachother in a predetermined configuration; positioning one or morerecording electrodes on a skin surface remote from the stimulationelectrodes at a location on the bottom of the subject's foot near theabductor hallucis and the flexor hallucis brevis muscles to recordelectromyogram (EMG) responses that result from recruitment of thetibial nerve's motor fibers; stimulating the tibial nerve by applyingelectrical stimulation pulses via the plurality of stimulationelectrodes according to stimulation parameters under closed-loop controlin which EMG responses elicited a predetermined time after applying theelectrical stimulation pulses are monitored via the recording electrodesand the stimulation parameters are adjusted in response to the monitoredEMG responses; and in response to detecting an unacceptable condition ofthe recording electrodes, applying electrical stimulation pulses via thestimulation electrodes according to the stimulation parameters underopen-loop control in which the stimulation parameters are maintainedwithout adjustment.
 2. The method recited in claim 1, wherein theunacceptable condition of the recording electrodes comprises anunacceptable impedance of the recording electrodes.
 3. The methodrecited in claim 1, wherein the step of applying electrical stimulationpulses further comprises monitoring for mechanomyogram (MMG) responsesto the electrical stimulation pulses and applying the electricalstimulation pulses under closed-loop control in which the stimulationparameters are adjusted in response to the monitored MMG responses. 4.The method recited in claim 1, wherein the step of applying electricalstimulation pulses comprises detecting impedances of the recordingelectrodes and, in response to detecting acceptable impedances of therecording electrodes, applying the electrical stimulation pulses.
 5. Themethod recited in claim 1, further comprising: obtaining samplemeasurements via the recording electrodes; checking the samplemeasurements for noise; checking the sample measurements for voluntaryEMG responses; applying the electrical stimulation pulses underclosed-loop control in response to determining an acceptable level ofnoise and the absence of voluntary EMG responses; and applying theelectrical stimulation pulses under open-loop control in response todetermining an unacceptable level of noise or the presence of voluntaryEMG responses.
 6. The method recited in claim 1, wherein eachapplication of an electrical stimulation pulse under closed-loop controlcomprises: applying the electrical stimulation pulse; recording, via therecording electrodes, EMG responses occurring the predetermined timeafter applying the electrical stimulation pulses; and adjusting thestimulation parameters in response to the recorded EMG responses.
 7. Themethod recited in claim 1, wherein the duration of the predeterminedtime is about 5 ms or less.
 8. The method recited in claim 6, whereinadjusting the stimulation parameters in response to the recorded EMGresponses under closed loop control comprises: increasing the amplitudeof subsequent stimulation pulses in response to the recorded EMGresponses being below a predetermined EMG window; decreasing theamplitude of subsequent stimulation pulses in response to the recordedEMG responses being above the predetermined EMG window; and maintainingthe amplitude of subsequent stimulation pulses in response to therecorded EMG responses being within the predetermined EMG window.
 9. Themethod recited in claim 1, wherein each application of an electricalstimulation pulse under open-loop control comprises: applying theelectrical stimulation pulse; and executing a time delay having aduration sufficient to maintain a constant stimulation period.
 10. Themethod recited in claim 9, wherein the duration of the time delay isabout 75 ms.
 11. The method recited in claim 1, wherein the step ofstimulating the tibial nerve by applying electrical stimulation pulsesvia the plurality of stimulation electrodes comprises selecting astimulation electrode pattern from a pattern list, wherein the methodfurther comprises generating the pattern list by: a) identifying a setof predetermined stimulation electrode patterns, each stimulationelectrode pattern identifying which of the plurality of stimulationelectrodes will apply the electrical stimulation pulses, and eachstimulation electrode pattern having associated with it the stimulationparameters according to which it applies stimulation pulses; b)selecting a stimulation electrode pattern from the set of predeterminedstimulation electrode patterns; c) generating a stimulation pulse usingthe selected stimulation electrode pattern according to its associatedstimulation parameters; d) determining via the recording electrodeswhether the stimulation pulse using the selected stimulation electrodepattern elicited an EMG response; e) adding the selected stimulationelectrode pattern to the pattern list in response to detecting an EMGresponse; f) omitting the selected stimulation electrode pattern fromthe pattern list in response to not detecting an EMG response; andrepeating steps b) through f) for each stimulation electrode pattern inthe set of predetermined stimulation electrode patterns to complete thepattern list.
 12. The method recited in claim 11, further comprisingoptimizing the stimulation electrode patterns in the pattern list by: g)adjusting the stimulation parameters for each stimulation electrodepattern in the pattern list to attempt to elicit an improved EMGresponse; h) selecting a stimulation electrode pattern from the set ofpredetermined stimulation electrode patterns; i) generating astimulation pulse using the selected stimulation electrode patternaccording to its associated stimulation parameters; j) determining viathe recording electrodes whether the stimulation pulse using theselected stimulation electrode pattern elicited an EMG response; k)adding the selected stimulation electrode pattern to the pattern list inresponse to detecting an EMG response; l) omitting the selectedstimulation electrode pattern from the pattern list in response to notdetecting an EMG response; and repeating steps h) through l) for eachstimulation electrode pattern in the set of predetermined stimulationelectrode patterns to complete the pattern list.
 13. The method recitedin claim 12, further comprising repeating steps of claim 12 until eachelectrode pattern in the pattern list is optimized.
 14. The methodrecited in claim 11, further comprising ordering the stimulationelectrode patterns in the pattern list according to their elicited EMGand/or MMG responses.
 15. A system for treating overactive bladder byapplying transcutaneous electrical stimulation to the tibial nerve of asubject, comprising: a plurality of electrical stimulation electrodes,the stimulation electrodes being spaced from each other in apredetermined configuration; one or more recording electrodes; astructure for supporting the stimulation electrodes and the recordingelectrodes spaced apart from each other; and a control unit forcontrolling the operation of the stimulation electrodes and therecording electrodes, wherein the control unit is configured to performthe method of claim
 1. 16. A system for treating overactive bladder byapplying transcutaneous electrical stimulation to the tibial nerve of asubject, comprising: a plurality of electrical stimulation electrodes,the stimulation electrodes being spaced from each other in apredetermined configuration; one or more recording electrodes; astructure for supporting the stimulation electrodes and the recordingelectrodes spaced apart from each other; and a control unit forcontrolling the operation of the stimulation electrodes and therecording electrodes, wherein the control unit is configured to performthe method of claim 11.